A couple praised by everyone around them, Maya and Yuu have recently started living together, their love for each other growing deeper than ever. One day, Yuu's younger sister, Kokoa, decides to leave her hometown and move to Tokyo. Overjoyed at seeing her sister again, Yuu welcomes her warmly, while Maya sincerely opens her heart to her new sister-in-law. However, Kokoa has ulterior motives. As she casually remarks, "I always want to take things that belong to others," she sets her sights on Maya, her sister's lover, and steadily advances her plans. As the day of her move draws near, the relationship between the two girls is about to undergo a drastic transformation.